Chapter 6 - Exchange Flashcards
Who has a larger surface area to volume ratio out of a mouse and an elephant?
Mouse
What are the 2 possible scenarios that might be asked about in relation to surface area to volume ratio
- The absorption of oxygen in single celled organisms
- Heat conservation/loss between mammals
How does extreme enter a single celled organism or a flatworm
Direct diffusion
What is a single celled organisms SA:VOL like
And how does oxygen diffuse into it
Very high SA:VOL
O2 observed through membrane
What does it mean if a mammal has a higher SA:VOL than another?
They lose more heat per gram of body weight
What does a mammal have to do if it loses more heat per gram of body mass
- Requires a faster rate of respiration
- As it needs more oxygen to maintain body temperature
How does an elephants rate of respiration differ to a mice?
Elephants is slower as they don’t need as much oxygen to maintain body temperature due to a smaller SA:VOL
What does the rate of diffusion for gas exchange depend upon? (Fick’s law)
Surface area of membrane
Diffusion distance (thickness)
Concentration gradient
What is fick’s law
Rate of diffusion is proportional to
Surface area x concentration difference/diffusion distance
Explain how gas exchange occurs in insects
- Air enters through spiracles into trachea
Trachea divide into tracheoles - Oxygen diffuses does concentration gradient along tracheoles
- Tracheoles are closely surrounded by cells so oxygen diffuses into cells
- Ventilation occurs, where air in trachea and tracheoles is replaced to maintain concentration gradient of oxygen between air and cells
What are examples of water loss adaptations in insects
- Body is covered by waxy cuticle to reduce evaporation
- Insects can close spiracles
Why are insects not able to grow to a large size?
Insects rely on diffusion to exchange gases directly between the environment and its cells, therefore a short diffusion pathway is needed
This means that they can’t grow to a much larger size
What is the way in which gas exchange in fish occurs referred to as
Counter current flow
What is meant by counter current flow
Water and blood moving in opposite directions
What is the purpose of counter current flow
- A high concentration gradient can be maintained across the entire surface, water is always next to blood with a low oxygen concentration
What are some adaptations that increase efficiency of diffusion in fish
- Filaments and lamellae have a large surface area
- Thin epithelium(short diffusion distance
- Circulation of blood, means that deoxygenated blood replaces oxygenated blood to maintain concentration gradient
- Ventilation of water means that oxygen is not lost by diffusing back into water
What are dicotyledonous plants
Plants with leaves
Explain gas exchange in dicotyledonous plants
- Air enters through stomata
- Gas exchange of CO2 and O2 occurs in mesophyll
What is an adaptation of mesophyll and why is this
They are spongy, so can increase surface area
How are dicotyledonous plants adapted to reduce water loss and how does this happen
- Guard cells can open and close stomata
- If a plant has a lot of water, cells are hard
- If it has a lack of water, cells are flacid, and if guard cells are flacid they close the stomata
What is a xerophytic plant
A plant in dry conditions eg cacti
What are 5 adaptations of xerophytic plants
- Curled leaves (spikes)
- Stomata sunken in pits
- Hairs on epidermis of leaf (bottom)
- Thick waxy cuticle
- Few stomata
How do curled leaves, sunken stomata and hairs on epidermis help to reduce water loss
- Reduces ventilation of air
- Therefore water vapour accumulates within the leaf (outside stomata)
- This decreases diffusion gradient for water vapour
- Reduces water loss
How does a thick waxy cuticle reduce water loss in xerophytic plants
- Reduces evaporation of water from leaf, thus reduces water loss
